1. Field of the Invention
The present invention relates to management of a stack of layer 2 switches configured for switching data packets.
2. Background Art
Local area networks use a network cable or other media to link stations on the network. Each local area network architecture uses a media access control (MAC) enabling network interface devices at each network node to access the network medium.
The Ethernet protocol IEEE 802.3 has evolved to specify a half-duplex media access mechanism and a full-duplex media access mechanism for transmission of data packets. The full-duplex media access mechanism provides a two-way, point-to-point communication link between two network elements, for example between a network node and a switched hub.
Switched local area networks are encountering increasing demands for higher speed connectivity, more flexible switching performance, and the ability to accommodate more complex network architectures. For example, commonly-assigned U.S. Pat. No. 5,953,335 discloses a network switch configured for switching layer 2 type Ethernet (IEEE 802.3) data packets between different network nodes; a received data packet may include a VLAN (virtual LAN) tagged frame according to IEEE 802.1q protocol that specifies another subnetwork (via a router) or a prescribed group of stations. The network switch includes multiple switch ports configured for sending and receiving data packets to respective network nodes according to IEEE 802.3 protocol, plus a management port that enables an external management entity to control overall operations of the switch using a management MAC interface. Hence, a host controller such as a host CPU can access the network switch chip via a standard MAC layer protocol.
FIG. 1 is a diagram illustrating a switch rack 10 having a stacked group of switches 12 for deployment of a local area network, managed by a remote management station 20. Each switch 12 has an integrated multiport switch 14 as disclosed in U.S. Pat. No. 5,953,355, plus a corresponding host CPU 16 for controlling the corresponding integrated multiport switch 14. Remote management software executed by the remote management station 20 manages the switches 12 by instructing a master CPU to read and write control/status registers in the switch chips 14. The switch rack 10 also includes a CPU bus 18 configured for communications between the CPUs 16, and an backbone link 22 for transfer of data frames between the integrated multiport switches 14. In particular, one of the CPUs 16a is designated as the master CPU and the remaining CPUs (e.g., 16b) are designated as slave CPUs, eliminating the necessity for the remote management station 20 to communicate with each of the individual CPUs 16. Hence, the remote management station 20 need only communicate with the master CPU 16a, with the master CPU 16a controlling the remaining slave CPUs (e.g., writing information into CPU control/status registers) via the CPU bus 18.
Use of the CPU bus 18, however, increases the required pin count of the CPUs 16, and the complexity of the switch rack 10.
There is a need for an arrangement that enables communication between multiple host processing units, configured for controlling respective network switch devices, without the necessity of a separate CPU bus.
These and other needs are attained by the present invention, where a switching system includes switches, each having a host processing unit and a switching unit, and a backbone link configured for transferring data packets between the switching units. One of the host processing units is configured as a master unit for generating a data frame having a destination address for a selected one of the switching units of a corresponding selected one of the other host processing units. The master unit outputs the data frame to the corresponding switching unit for transfer to the selected one switching unit via the backbone link. The selected one switching unit, in response to receiving the data frame having the corresponding destination address, forwards the data frame to the corresponding host processing unit for execution of a processing operation specified in the data frame. Hence, the switching system provides inter-processor communications using a preexisting backbone link, eliminating the necessity of a processor bus.
One aspect of the present invention provides a method in a network switching system having multiple switching units controlled by respective host processing units. The method includes generating a data frame by a first of the host processing units, configured as a master unit, by including a destination address of a selected one of the switching units controlled by a corresponding selected one of the other host processing units. The method also includes outputting the data frame from the master unit to the corresponding switching unit, transferring the data frame from the switching unit having received the data frame from the master unit to the selected one switching unit via a backbone link, and forwarding the data frame from the selected one switching unit to the corresponding selected one other host processing unit, for execution of a processing operation specified in the data frame, based on the selected one switching unit detecting the destination address matching an assigned address of the selected one switching unit.
Another aspect of the present invention provides a switching system configured for receiving commands from a remote manager. The system includes switches and a backbone link. Each switch has a switching unit, having an assigned network address, and a corresponding host processing unit configured for controlling the corresponding switching unit. One of the host processing units is configured for receiving a command from the remote manager and in response generating a data frame having a destination address for configuration of a selected one of the switching units by the corresponding selected one of the other host processing units. Each switching unit is configured for forwarding a received data frame having a matching destination address to the corresponding host processing unit. The backbone link is configured for transferring the data frame from the switching unit corresponding to the one host processing unit to the selected switching unit, and the selected one other host processing unit is configured for executing a processing operation specified in the data frame based on retrieval of the data frame from the corresponding selected switching unit.
Additional advantages and novel features of the invention will be set forth in part in the description which follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the present invention may be realized and attained by means of instrumentalities and combinations particularly pointed in the appended claims.